Water jacketed cylinder liners having annularly spaced air inlet ports intermediate their ends are known in the internal combustion engine art. Such liners are commonly made from an alloy cast iron having a medium hardness, as cast, in the range of from about 200 to 260 Brinell. It is also known in such liners to provide a diametrically relieved area of the bore at the ports and extending axially on either side thereof. This port relief area is smoothly curved and blended into the upper and lower liner bores and helps reduce scuffing originating in the port areas and resulting from the rubbing contact in service of the walls of an associated piston and its rings with the cylinder liner bore and port area.
Various other methods have been employed to reduce cylinder liner scuffing. One such method for improving a cylinder liner to reduce scuffing involves plating the cylinder liner with a hard material such as chromium. However, this method is not generally desired because of cost.
Another method of improving a cylinder liner to reduce scuffing involves laser hardening scuff prone surfaces of the bore. However, since lasers are commonly focused into a small diameter beam, the laser must make multiple passes or closed helical passes over the surface of the bore to adequately heat and fully harden the scuff prone surfaces of the bore. As a result, laser hardening is a costly and time consuming method.
Another method of improving a cylinder liner to reduce scuffing involves induction hardening scuff prone surfaces of the bore. Induction hardening uses an electromagnetic coil, which rapidly heats adjacent surfaces of the bore to a hardening temperature. However, when a coil is used around the intake ports and the relieved areas of the cylinder bore, the varying dimensions and geometry of the intake ports and the relieved areas can create difficulties in the hardening process, in that the portions of the bore nearest the coil heat at a faster rate than the portions of the bore farthest from the coil. As a result, the surfaces farthest from the coil may not reach hardening temperature, causing inconsistencies in the quality of the heated surfaces.